Cortical sensory maps are important for perceptual learning. Cortical inhibition has an important role in the formation, maintenance and adaptability of these maps. We hypothesize that long-term potentiation (LTP) of thalamocortical synapses onto inhibitory neurons is important for the refinement of sensory maps. Specific Aim 1: The first aim of this study is to determine if LTP can be elicited at thalamocortical synapses onto inhibitory neurons. Specific Aim 2: The aim of this experiment is to determine if LTP is dependent on NMDA receptors, calcium-permeable AMPA receptors, metabotropic glutamate receptors or L-type voltage dependent calcium channels, using selective receptor antagonists. Specific Aim 3: The aim of this expedment is to determine if LTP of thalamic inputs onto inhibitory neurons is dependent on a critical period. The results of this project will increase our understanding of the mechanisms involve in perceptual learning.